Novel method of dual fiber Bragg gratings integrated in fiber ring laser for biochemical sensors

Abstract

Optical sensors have been shown to be very effective for measuring the toxic content in liquid and air environments. Optical sensors, which operate based on the wavelength shift of the optical signals, require an expensive spectrometer. In this paper, we propose a new configuration of the optical sensor device for measuring wavelength shift without using a spectrometer. This configuration has a large potential for application in biochemical sensing techniques, and comes with a low cost. This configuration uses dual fiber Bragg gratings (FBGs) integrated in a fiber ring laser structure of erbium-doped fiber, in which one FBG is used as a reference to sweep over the applicable spectrum of the etched-Bragg grating. The etched-FBG as a sensing probe is suitable for bio- and/or chemical sensors. The sensitivity and accuracy of the sensor system can be improved by the narrow linewidth of emission spectra from the laser, the best limit of detection of this sensor is 1.5 × 10−4 RIU (RIU: refractive index unit), as achieved by the optical sensor using a high resolution spectrometer. This sensor system has been experimentally investigated to detect different types of organic compounds, gasoline, mixing ratios of organic solvents in gasoline, and nitrate concentration in water samples. The experimental results show that this sensing method could determine different mixing ratios of organic solvents with good repeatability, high accuracy, and rapid response: e.g. for ethanol and/or methanol in gasoline RON 92 (RON: research octane number) of 0%–14% v/v, and nitrate in water samples at a low concentration range of 0–50 ppm. These results suggest that the proposed configuration can construct low-cost and accurate biochemical sensors.

Wavelength Shift Measurement Method Without Use of Spectrometer: The New Way for Environment Photonic Sensors

“…In experiment of the ring-cavity fiber laser combined with two FBGs, we used the re-FBG as the same characteristics as used in [14] (the Bragg wavelength at room temperature was in the range of 1530 ÷ 1550 nm and a reflectivity was 75 -90%; the full-width-half-maximum (FWHM) bandwidth of 0.15÷0.30 nm and FBG length of 15 mm). But the e-FBG fabricated by wet chemical etching only half part of fiber cladding of the FBG region in hydrofluoric acid (HF) solution for creating D-form of FBG-fiber to increase the interaction of the propagating optical field in the FBG with the surrounding medium, which is different form in comparison with e-FBG presented in previous works [14,17]. In the e-FBG and fiber ring laser combined configuration, the reflected light from e-FBG can be used to analyze the interaction between the evanescent wave and the surrounding medium by measuring wavelength shift of lasing emission.…”

“…For low-cost bio-chemical sensor, the configuration using dual fiber Bragg gratings (etched-FBG and reference-FBG) integrated in fiber ring laser structure is shown high sensitivity and effectively for determination of bio-chemical agents in liquid environment [13,14]. The sensing signal is demodulated the central wavelength shift of the e-FBG on the basis of the lasing power when lasing signal of the re-FBG is swept over the spectrum of the e-FBG by using the Peltier cooler that applies temperature on the re-FBG.…”

“…A light emitted from broadband amplified spontaneous emission of erbium ions enters the re-FBG through a circulator 1, and the reflection spectrum of re-FBG then propagates back through the circulator 1 again to the circulator 2, where the reflected signal is entered the e-FBG then filtered and reflected again into loop-cavity. The laser emission is directed out by a fiber-optic coupler 10/90 in order to extract 10% of the light from the cavity to be detected by a photo-detector, and 90% of the light comes back to the laser cavity loop [14].…”

“…Schematic diagram of the low-cost bio-chemical sensor using dual fiber Bragg gratings (e-FBG and re-FBG) integrated in fiber ring laser configuration[13,14].…”

Simultaneous Measurement of Temperature and Relative Humidity Using a Dual-Wavelength Erbium-Doped Fiber Ring Laser Sensor

“…The high OSNR in FRLs enables remote detection of a particular target measurement at long distance and improves the detection accuracy. Due to high OSNR, low spectral width and high intensity FRLs are of great research interest [20][21][22][23][24][25][26][27][28][29][30]. Different structures had been proposed within FRL setups for sensing applications, i.e.…”